[1]} and [2]} showed that \(\hat{\theta }_{OLS}\)  is also a consistent estimator of \(\theta _{L^2}\) . Furthermore, \(\hat{\theta }_{OLS}\)  has the following asymptotic normal distribution
\(\hat{\theta }_{OLS}\sim \mathrm {N}\left(\theta _{L^2}, V^{-1} W_{OLS} V^{-1} \right),\) 
